Crash course in collision

Impact phenomena can be associated with or classified according to a wide range of prevailing conditions and possible consequences. A considerable amount of knowledge has been generated by studying the impact problems arising in physics and engineering from every possible angle.

Regarding the consequences of impact, for instance, particular attention has been given to the local, often catastrophic geometric and material changes leading to penetration, erosion or structural collapse.

Bill Stronge’s Impact Mechanics is concerned mainly with the changes in the global kinematics of impacting bodies. Thus, contact interaction considerations are in essence limited to local, contained and, therefore, relatively small deformation. For this type of problem, either the velocity of impact should be low or the colliding bodies should be hard. These assumptions define more or less the scope of the book. It should also be noted that Impact Mechanics is intended as a textbook, which is another self-imposed limitation on the fully comprehensive treatment of such a complex subject. For instance, there is no reference to the special treatment of global dynamics arising in maritime collisions.

Within its well-defined scope, the subject matter is addressed in a mature, thorough and mathematically rigorous manner. Fundamental principles and other relevant theoretical results are elaborately introduced so that the reader does not require frequent recourse to other sources of related knowledge from the wider field of mechanics. Solved examples and homework problems allow the readers to test their understanding of the material. The book is self-contained, and its aim to instruct is, to a great extent, successfully met.

Contained local interaction is thoroughly explored. It also employs continuum elastic and elasto-plastic, as well as discrete viscoelastic, deformation models to develop analyses for the prediction of momentum changes and energy transfers between colliding bodies. Oblique impact and its implications for contact compliance, friction and slip are also rigorously treated in two and in three dimensions.

Compilation and presentation of material related to these aspects of the phenomenon are apparently original, reflecting the author’s own research interests. Other interesting topics not commonly found in impact treatises but discussed in some detail in this book are mathematical models of impact involving assemblies of loosely connected rigid bodies as well as sequential or propagating impact events, such as the domino effect. Inclusion of such material extends the scope of Impact Mechanics beyond that of a standard textbook.

Another attractive feature of the book is the inclusion of a brief but informative historical chapter, discretely placed at the end of the book, which further motivates the reader to indulge in the subject while offering relief from the rather mathematical content of the remainder of the book.

Regarding style and structure of presentation, only minor criticisms can be made, relating mostly to occasional inconsistencies in notation. The main text is written with sufficient detail and clarity, although some solved examples are presented in a rather laconic manner, anticipating a well-informed reader.
 
This hints at the kind of expected readership. The book is, in essence, addressed to motivated students on advanced specialised courses or relevant research programmes. But it does initiate discussion on the treatment of more complex impact problems that could be encountered in practice. Because of its comprehensive treatment of relevant fundamental material, such as contact mechanics, vibrations and wave propagation, the book could also prove appealing to a wider readership of engineering and science specialists in related fields who wish to acquire a more global knowledge and understanding of such interrelated problems.

Stavros Syngellakis is senior lecturer, school of engineering sciences, University of Southampton.